In the last two issues of this UA Vegetable IPM Newsletter, I have presented a melon (Cucumis melo ‘reticulatus’ L.) crop phenology model (Figure 1; Silvertooth, 2025a) based on actual heat unit accumulations (86/55 ºF thresholds). This model can be useful in predicting and tracking crop development and identifying important stages of crop growth and development (crop phenology).
Referring to the data from AZMET for several locations in the Yuma area, the HU accumulations from 1 January 2025 for a set of four possible 2025 planting dates are listed in Table 1. The HU accumulations from 1 January 2025 to 28 April 2025 for these sites are listed in Table 2.
The HU accumulations after planting (HUAP) for these four possible planting dates for three Yuma area locations to 28 April 2025 are shown in Table 3. The HUAP values in Table 3 are simply the difference between the values in Tables 1 and 2.
An example for the Yuma Valley, 15 January 2025 planting date is: HU from 1 January to 28 April 1096 - 73 HU accumulated at planting on 15 January = 1023 HUAP for this case.
The information in Table 3 can help serve as a reference to check for melon crop
development in the field against this phenological model in Figure 1. In the most edition of this newsletter (Silvertooth, 2025b) the projected stages of growth were presented based on this phenological model and current HU accumulations.
Based on this phenology model and current HU accumulations for this season we should be able to make some projections on the current stage of growth, which we can go to the field and check. For example, for melon fields in the lower Colorado River Valley at this time, we can expect to find fields planted and watered up in mid-January to have crown set melons maturing and approaching harvest conditions. These fields could have crown fruit ready for harvesting in about three weeks, based on these projections and normal HU accumulation patterns for this time of year. For fields planted and wet dates near the first of March, these fields should have small crown set melons approaching golf ball size.
Table 1. Heat unit accumulations (86/55 ºF thresholds) after 1 January 2025 on four
possible 2025 planting dates utilizing Arizona Meteorological Network (AZMET) data for
each representative site.
Yuma Valley: https://azmet.arizona.edu/application-areas/heat-units/station-level-summaries/az02
Yuma North Gila: https://azmet.arizona.edu/application-areas/heat-units/station-level-summaries/az14
Roll: https://azmet.arizona.edu/application-areas/heat-units/station-level-summaries/az24
Table 2. Heat unit accumulations (86/55 ºF thresholds) after 1 January 2025 to 14
April 2025 utilizing Arizona Meteorological Network (AZMET) data for each
representative site.
Table 3. Heat unit accumulations (86/55 ºF thresholds) after planting (HUAP) from four
possible 2025 planting dates and three sites in the Yuma area on 30 April 2025 utilizing
Arizona Meteorological Network (AZMET) data for each representative site. Each value
is rounded to the next whole number. Note: the values in Table 3 are determined by
taking the difference between the HUs for each representative site and four planting
dates in Tables 1 and 2.
Figure 1. Melon (cantaloupe) phenological development model expressed in Heat Units
Accumulated After Planting (HUAP, 86/55 oF).
At events and in the halls of the Yuma Agricultural Center, I’ve been hearing murmurings predicting a wet winter this year…
As the Yuma Sun reported last week, “The storms of Monday, Aug. 25 [2025], were the severest conditions of monsoon season so far this year in Yuma County, bringing record-rainfall, widespread power outages and--in the fields--disruptions in planting schedules.”
While the Climate Prediction Center of the National Weather Service maintains its prediction of below average rainfall this fall and winter as a whole, the NWS is saying this week will bring several chances of scattered storms.
These unusually wet conditions at germination can favor seedling disease development. Please be on the lookout for seedling disease in all crops as we begin the fall planting season. Most often the many fungal and oomycete pathogens that cause seedling disease strike before or soon after seedlings emerge, causing what we call damping-off. These common soilborne diseases can quickly kill germinating seeds and young plants and leave stands looking patchy or empty. Early symptoms include poor germination, water-soaked or severely discolored lesions near the soil line, and sudden seedling collapse followed by desiccation.
It is important to note that oomycete and fungal pathogens typically cannot be controlled by the same fungicidal mode of action. That is why an accurate diagnosis is critical before considering treatments with fungicides. If you suspect you have seedling diseases in your field, please submit samples to the Yuma Plant Health Clinic or schedule a field visit with me.
National Weather Service Climate Prediction Center: https://www.cpc.ncep.noaa.gov/
National Weather Service forecast: https://forecast.weather.govReferences
Jay-Russell, M.T. (2013). What is the risk from wild animalsin food-borne pathogen contamination of plants?. CABI Reviews 4(8),1-16.https://doi: 10.1079/PAVSNNR20138040
Fig. 1. Bird fecal matter on romaine lettuce.
Fig. 2. Gull flying over romaine lettuce being harvested.
Fig. 3. Gulls flying over irrigation canal near lettuce field
being harvested.
Fig. 4. Bird fecal matter on lettuce harvesting equipment.
We are receiving some summer grass samples for identification. As you know the seedlings look very similar.
PCAs have mentioned, and we can corroborate that some species respond differently to herbicides. As an example, we have seen that Sprangletop (Leptochloa filiformis) is not controlled with selective postemergent herbicides like Fusilade or Poast. We have seen only good results with a high rate of clethodim (Select), and the generics off the same active ingredient. Sandbur is also tolerant to these herbicides.
These two weeds frequently come back from crowns surviving the winter which makes spring preemergence herbicides applied ineffective.
The following are common species of summer annual grass here:
|
echinochloa |
water grass and barnyard grass |
|
leptochloa |
red sprangletop and mexican sprangletop |
|
eriochloa |
southwestern cupgrass and prairie cupgrass |
|
cenchrus |
field sandbur and red sandbur |
|
setaria |
green foxtail and yellow foxtail and |
|
chloris |
feather finger grass and truncate finger grass |
Check out the Summer Annual Grass ID publication which contains pictures and descriptive characteristics of each of these species.
Western Flower thrips is among the most economically important insect pests that infests desert lettuce. Bean thrips started to become a major pest of fall lettuce in the desert over the last decade. Our objective is to determine alternative organic insecticides that can be used as part of an IPM program targeting these pests in leafy vegetable crops.
This fall, at the YAC experimental farm, we evaluated 10 organic insecticides frothier efficacy in suppressing western flower thrips and bean thrips in organic head lettuce. M-Pede, Pyganic, and Aza-Direct were evaluated with Oroboost included in one treatment and Orbit DL included in the other treatment. Thus, we evaluated these aforementioned insecticides in two different treatment entries. The purpose was to understand the performance of these insecticides with Orbit DL or Oroboost as adjuvant. The remaining insecticide treatments had only Oroboost as adjuvant. Both Oroboost and Orbit DL are OMRI approved organic adjuvants.
We expected that several of these bioinsecticides would exhibit some measurable level of thrips suppression. However, our data showed that only Entrust exhibited measurable reduction in immature thrips, western flower thrips, and bean thrips numbers (Fig. 1-3). Gargoil and Pyganic with the Orbit as adjuvant exhibited a slight reduction in western flower thrips adults (Fig. 2). We will continue to evaluate these organic insecticides against the thrips to gather more research-based evidence which will allow us to draw more accurate conclusions and make relevant recommendations.
Figure 1. Mean thrips nymph/plant as affected by organic insecticide application.
DAT=Day After Treatment.
Figure 2. Mean western flower thrips adult/plant as affected by organic insecticide
application. DAT=Day After Treatment.
Figure 3. Mean bean thrips adult/plant as affected by organic insecticide application.
DAT=Day After Treatment.
Organic farming faces two major challenges: weeds, which remain the number one concern, and insect pressures that can severely affect crop quality and yields. Effective strategies for managing weeds and insects are critical, especially as organic production expands. Traditionally, these tasks have been labor-intensive and time-consuming, creating a strong need for innovative solutions that can improve efficiency while maintaining crop standards. With the current momentum for increased AI integration into agriculture supported by both industry and Washington D.C., novel technologies AICropCAM present exciting opportunities for leafy green growers. These high-tech platforms could offer early-stage detection of weeds and insects, helping growers respond more quickly and precisely. Such innovations have the potential to save significant time and labor, particularly across large acreages, while improving overall crop management decisions.
What is AICropCAM, and How Does it Work?
AICropCAM (Figs. 1, 2, & 3) is an advanced edge image processing platform designed to extract plant and canopy features directly from field crops. Its structure includes three key layers:
One of AICropCAM’s biggest advantages is its ability to perform deep learning-based image processing directly in the field. This means it can detect subtle signs of weed emergence or insect damage in real-time, capturing critical information that traditional imaging or simple sensors often miss. Edge computing also significantly reduces the need for high-bandwidth data transmission, a major limitation in rural agricultural areas.
Looking Ahead
Incorporating AICropCAM into leafy green production systems could help growers proactively manage weeds and insect pressures, optimize resource use, reduce chemical interventions (especially important in organic systems), and save time and labor. These technologies offer a glimpse into the future of precision agriculture, where early detection and informed decision-making can significantly boost sustainability and profitability.
Figure 1 (left): AICropCAM-insect detection, Figure 2 (middle): AICropCAM-weed
detection, Figure 3 (right): AICropCAM-installed in the field.
Results of pheromone and sticky trap catches can be viewed here.
Corn earworm: CEW moth counts down in most over the last month, but increased activity in Wellton and Tacna in the past week; above average for this time of season.
Beet armyworm: Moth trap counts increased in most areas, above average for this time of the year.
Cabbage looper: Moths remain in all traps in the past 2 weeks, and average for this time of the season.
Diamondback moth: Adults decreased to all locations but still remain active in Wellton and the N. Yuma Valley. Overall, below average for January.
Whitefly: Adult movement remains low in all areas, consistent with previous years.
Thrips: Thrips adults movement decreased in past 2 weeks, overall activity below average for January.
Aphids: Winged aphids are still actively moving, but lower in most areas. About average for January.
Leafminers: Adult activity down in most locations, below average for this time of season.
